Feedback compensation in a sound processing device

Abstract

There is disclosed a sound processing device ( 300 ) configured to apply a frequency shift to at least one frequency component of a received sound signal and to amplify at least part of the received sound signal. The processing device ( 300 ) is also adapted to generate an estimated feedback signal for combination with the received sound signal via a phase inverting feedback canceller ( 314 ). Associated methods ( 400, 600 ) of processing a sound signal are also disclosed.

1. A method of processing a sound signal in a sound processing device, the method including:
 (a) receiving an input sound signal; 
 (b) applying a frequency change to one or more frequency components of the input sound signal, at least intermittently; 
 (c) amplifying at least a portion of the input sound signal; 
 (d) generating an estimated feedback signal corresponding to a feedback path of the sound processing device at least when said frequency transposition is applied; and 
 (e) combining the input sound signal with a phase inverted representation of the estimated feedback signal to cancel feedback from the input sound signal. 
 
     
     
       2. A method of processing a sound signal according to  claim 1  wherein the frequency change is selectively activated or deactivated. 
     
     
       3. A method of processing a sound signal according to either of  claims 1  or  2  wherein the method further includes:
 classifying the input sound signal; 
 applying a frequency transposition activation scheme on the basis of said classification. 
 
     
     
       4. A method of processing a sound signal according to any one of  claims 1  to  3  wherein during a period in which a frequency change is applied to one or more frequency components of the input sound signal, steps (d) and (e) are performed such that the feedback cancellation is performed with a first adaptation speed. 
     
     
       5. A method of processing a sound signal according to  claim 4  wherein during a period in which a frequency change is not applied, steps (d) and (e) are performed such that the feedback cancellation is performed with a second adaptation speed. 
     
     
       6. A method of processing a sound signal according to  claim 5  wherein the first adaptation speed is faster than the second adaptation speed. 
     
     
       7. A method of processing a sound signal according to any one of  claims 1  to  6  wherein estimated feedback signal is generated on the basis of an output of at least one of: the sound processing device; a sound receiving stage of the sound processing device; a frequency transposition stage of the sound processing device; and an amplification stage of the sound processing device. 
     
     
       8. A sound processing device including:
 a sound receiving stage for receiving a sound signal; 
 frequency transposition stage for applying frequency change to at least one frequency component of the received sound signal; 
 an amplification stage configured to amplify at least part of the received sound signal; 
 a feedback estimation stage configured to generate an estimated feedback signal on the basis of an output of at least one of the sound receiving stage, the frequency transposition stage, the amplification stage and the sound processing device; and 
 a phase inverting feedback cancelling stage configured to combine the estimated feedback signal with the input signal to cancel a feedback component of the sound signal received at the sound receiving stage. 
 
     
     
       9. A sound processing device according to  claim 8  which further includes frequency transposition activation stage configured to activate and/or deactivate the frequency transposition stage. 
     
     
       10. A sound processing device according to either one of  claims 8  or  9  wherein a rate of feedback estimation of the feedback estimation stage is variable. 
     
     
       11. A sound processing device according to  claim 10  wherein the feedback estimation stage is configured to estimate the feedback signal at a first rate when the frequency transposition stage is activated. 
     
     
       12. A sound processing device according to  claim 11  wherein the feedback estimation stage is configured to estimate the feedback signal at a second rate when the frequency transposition stage is inactive. 
     
     
       13. A sound processing device according to  claim 12  wherein the first rate is higher than the second rate. 
     
     
       14. A sound processing device according to any one of  claims 9  to  13  wherein the device further includes a sound classification stage configured to classify the received sound signal and cause the frequency transposition activation stage to control the operation of the frequency transposition stage in accordance with one of a plurality of frequency transposition activation schemes. 
     
     
       15. A sound processing device according to  claim 14  wherein the frequency transposition activation stage is configured to periodically activate the frequency transposition stage. 
     
     
       16. A sound processing device according to  claim 15  wherein the frequency transposition activation stage is configured to activate the frequency transposition stage at an activation rate dependent upon the determined classification of the received sound signal. 
     
     
       17. A sound processing device according to  claim 15  wherein a duration of activation of the frequency transposition stage is determined on the basis of the determined classification of the received sound signal. 
     
     
       18. A sound processing device according to any one of the preceding claims wherein the sound receiving stage is configured to receive either an acoustic signal or data signal representing an acoustic signal.